This invention relates to a V-belt used for power transmission to drive accessory units to an automotive internal combustion engine.
FIG. 1 shows a prior art arrangement in which a V-belt to which the invention pertains is used. This arrangement shows a crankshaft pulley 1a for taking out power from an engine 1b, a drive pulley 2a of an automotive generator 2b for charging a battery (not shown) and driving automotive electric units such as lamps and horns, a drive pulley 3a of an engine cooling water circulating pump or a cooling fan 3b, and a V-belt 4. The V-belt 4 serves to transmit the engine power through the crankshaft pulley 1a to the fan and generator.
The automotive V-belt is used under different working conditions from those for the general industrial belts. More particularly, automotive V-belts run at higher speeds and bear higher loads. Further, pulleys are installed in narrow spaces and therefore have small diameters, so that the angles of contact between belt and pulley are small. Further, they are used in severe environments in view of high temperature, dust and vibrations. Therefore, they are subject to extreme elongation and other deformations, which is undesired from the standpoint of their useful life. Particularly, attachment of dust to the belt does not only curtail belt life, but also promotes wear of the pulleys of the accessory units.
FIGS. 2 and 3 show prior art examples of V-belts of this kind. The example of FIG. 2 comprises a cover cloth 5, a rubber layer 6 which takes up tensile force applied to the belt, reinforcing members 7 for preventing elongation of the belt, a rubber layer 8 in which the reinforcing members are buried and a rubber layer 9 which takes up compressive force applied to the belt. The example of FIG. 3 comprises a top cloth 10, rubber layers 8 and 9, ropes 11 used as reinforcing members and a reinforcement bottom cover 12.
As shown, the prior art V-belts use a cover cloth which covers either the entire periphery or only the top of the belt. In either case, a tension necessary for power transmission is given. These V-belts are used in very severe conditions, and their sides are worn extremely due to slip, bending, side pressure and heat generation, so that their useful life is short. In addition, dust is liable to be attached to them, adversely affecting the pulleys of accessory units.